Degradation of polymer electrolyte membrane fuel cell (PEMFC) systems has emerged as a critical issue. A thin metal oxide layer coated with Pt/carbon via ALD (atomic layer deposition) is one of the potential approaches for preserving electrochemical activity; however, the exact interfacial effects of metal oxide on enhancing PEMFC durability are unclear. Herein, interfacial engineering of the TiO 2 layers within the in situ-synthesized Pt/carbon catalysts (Pt/TiO 2 /C and TiO 2 /Pt/C) was studied using fluidized bed reactor (FBR) ALD to investigate the exact effects of the catalysts. For the Pt/TiO 2 /C catalyst, the TiO 2 layer was first conformally coated on the carbon surfaces, whereas for TiO 2 /Pt/C, the TiO 2 layer was selectively formed on the Pt NP surface via the ALD mechanism. The Pt/TiO 2 /C catalyst has a higher Pt loading with suppressed micropores due to the introduction of the TiO 2 layer on the carbon support, whereas the TiO 2 /Pt/C catalyst remained in the 2−3 nm mesopores. The electrochemical durability of both ALD catalysts is superior to that of the commercial Pt catalyst. Encapsulating the TiO 2 layer on the Pt surface specializing in blocking Pt dissolution resulted in better long-term stability of the electrochemical characteristics compared to the stability of those of Pt/TiO 2 / C, which especially showed the better initial performance of the electrochemically active surface area, oxygen reduction reaction, and PEMFC single-cell performance. This study provides the direction and steps toward an efficient nanostructure design of metal oxide by ALD in most catalyst fields.
Recently developed fabrication methods for inorganic patterns (such as laser printing and optical lithography) can avoid some patterning processes conducted by conventional etching and lithography (such as substrate etching and modulation) and are thereby useful for applications in which the substrates and materials must not be damaged during patterning. Simultaneously, it is also necessary to develop facile and economical methods producing inorganic patterns on various substrates without requiring a special apparatus while attaining the above-mentioned advantages. The present study proposes a reaction-based method for fabricating inorganic patterns by immersing substrates coated with a colloidal nanosheet into an aqueous solution containing inorganic precursors. Silica and TiO 2 patterns spontaneously developed during the conversion of each inorganic precursor. These patterns were successful on rigid and flexible substrates. We fabricated these patterns on a wafer-sized silicon and large flexible poly(ethylene terephthalate) film, suggesting the scalability. We fabricated a biomimetic pattern on both sides of a glass window, as a photovoltaic roof, for minimal optical losses to maximally present photovoltaic effects of a solar cell. The TiO 2 pattern on glass window exhibits sustainable sunlight-driven-cleaning activity for contaminants. The method could provide a platform for economical high-performance inorganic patterns for energy, environmental, electronics, and other areas. KEYWORDS: reaction-based inorganic patterning, silica and TiO 2 patterns, patterns on both sides of substrates, solar cell roof, sustainable self-cleaning window
The 0.5 mol% Er3+ doped TiO2 (Er(3+)-TiO2) nanofibers were synthesized by a sol-gel derived electrospinning and subsequent calcination for 3 h at 500 degrees C in air. The calcined fibers were examined to evaluate the effect of collector speed and flow rate on morphology of the fibers. The dynamic viscosity and surface tension of precursor solution were 34 cP and 22.7 mN/m, respectively. The Er(3+)-TiO2 nanofibers were electrospun horizontally on the drum rotated at 100-500 rpm and flow rate of 0.2-0.5 mL/h under a DC voltage of 10 kV. The grounded collector is a stainless mandrel placed 12 cm away from the tip of the needle. Beads were observed for the nanofibers prepared at flow rates from 0.2 mL/h to 0.5 mL/h when the collector speed was 100 rpm. The nanofibers increased in diameter slightly from 150 nm to 190 nm as the flow rate was raised from 0.2 mLh to 0.5 mL/h. No beads were found at the collector speed of above 300 rpm when the flow rate was 0.2 mL/h. The optimized flow rate and collector speed of the nanofibers were determined to be in the range of 0.2-0.3 mL/h and 300-400 rpm, respectively. Uniform, smooth and continuous fibers with diameters of 150 to 170 nm were detected. Crystallite size determined by the Scherrer formula was about 6 nm. It can be concluded that the collector speed and the flow rate are influential on the morphology of the Er(3+)-TiO2 nanofibers. The Er(3+)-TiO2 nanofibers, prepared at 0.2 mL/h and 300 rpm, had typical absorption peaks located at 490, 523 and 654 nm, corresponding to the transitions from 4I15/2 to 4F7/2, 2H11/2 and 4F9/2, respectively. The Er(3+)-TiO2 nanofibers showed enhanced photoresponses under visible light.
Due to the increase in incidence of infection of Mycobacterium tuberculosis complex (MTC), it is imperative that a rapid diagnosis accompanies the handling of MTC. This is due to the three to eight weeks it takes to culture Mycobacteria, and the lack of sensitivity of microscopic examination of AFB. Recently, nested PCR has been used to detect and diagnose mycobacteria. It is especially useful in complementing diagnosis by histological extra pulmonary. After culturing all the specimens and practicing the nested PCR, we did comparison analysis between nested PCR and culture. There were 76 specimens, 31 of which were positive. Of the 31 positive specimens in culturing, only 22 were positive in nested PCR. Of the 45 negative specimens, 36 were negative in nested PCR. As a result, Sensitivity was 71% and specificity was 80%. Furthermore, the positive predictive value was 71% and negative predictive value was 80%. These results indicate that nested PCR based techniques are sensitive, specific, and rapid methods for the detection of MTC.
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